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How Might New Neurons Buffer Against Stress?

Clues Emerging from Studies in New Porter Neuroscience Center

July 18, 2014 • Science Update

Over the past decade or so, evidence has emerged suggesting that the birth of new neurons in the adult brain’s memory hub, or hippocampus, may play a key role in the action of antidepressants, resilience to stress, the benefits of exercise and enriched environments, and preventing memory loss. But understanding how it might work has remained elusive.

Heather Cameron, Ph.D., chief of the NIMH intramural Unit on Neuroplasticity, discussed findings of ongoing studies on the function of adult neurogenesis in the hippocampus at a research symposium held in March, in conjunction with the formal dedication of the Porter Neuroscience Research Center on the NIH campus in Bethesda, MD, where her lab is located.

Cameron’s team devised a way to selectively stop the birth of new neurons in the hippocampus of adult mice without disturbing the surrounding cellular infrastructure. They genetically engineered a strain of mice harboring neurons that self-destruct if they try to divide.

To their surprise, the animals lacking new neurons performed as well as control mice on memory tasks. Only after looking more closely at the animals’ behavior during a water maze memory task did the researchers turn up a clue: Animals lacking neurogenesis were prone to circling the edge of the pool – a stress-related behavior.

If missing new neurons doesn’t cause a learning and memory deficit, might it alter the stress response? In a follow-up test, animals lacking neurogenesis showed abnormally prolonged increases in their stress hormone levels – the hormone levels took longer to return to baseline after the stress of being held in restraint for 30 minutes.

“This surprised us because there’s no learning or memory involved in this experiment,” said Cameron. If first stressed by restraint, animals lacking neurogenesis also took longer than control animals before venturing out into an open space for food – a depression-like behavior in rodents.

To better understand how having new neurons appears to buffer against stress effects on behavior, the NIMH researchers are now exploring other possible mechanisms involving stress-related thinking and emotion circuitry.

VIDEO A college student’s stint in a Porter neuroscience labHeather Frank, then a senior majoring in neuroscience at Colgate University, explains studies on neurogenesis that she worked on during an internship in the NIMH Unit on Neuroplasticity. The lab is located in the Porter Neuroscience Research Center, which was formally dedicated in Spring, 2014.

VIDEO Porter Building Dedication, March 31, 2014

NIH Director Francis Collins and several current and former Institute directors, including NIMH’s Drs. Thomas Insel and Steven Hyman, spoke at the dedication ceremony for the Porter Neuroscience Research Center, earlier this year.http://videocast.nih.gov/launch.asp?18358